There is a conventionally known heat exchanger of this type, the heat exchanger including: a pair of headers vertically arranged at an interval; a plurality of flat tubes arranged at intervals in a width direction of the heat exchanger, both ends of the tubes connected to peripheral surfaces of the headers respectively; and heat transfer fins provided between the tubes, wherein a heating medium is distributed between the headers through the tubes to exchange the heat of external air flowing outside of the tubes in a front and back direction and the heat of the heating medium in the tubes.
The heat exchanger includes a plurality of tube groups arranged in the front and back direction, and the heating medium sequentially flows from a front tube group to a back tube group through each header. In this case, there is a conventional heat exchanger including tank-like headers provided on each of one end side and the other end side of each tube group (for example, see Patent Literature 1), and there is a conventional heat exchanger including a plurality of core sections arranged in the front and back direction, the core sections including cylindrical headers provided on each of one end side and the other end side of the tube groups (for example, see Patent Literature 2).